Resist composition and organic solvent for removing resist

ABSTRACT

The present invention provides a resist composition comprising benzyl alcohol or its derivatives as an organic solvent. The present invention also provides an organic solvent for removing a resist, wherein the organic solvent comprises benzyl alcohol or its derivatives. The resist composition of the present invention is used in a lithography process for forming a micro-pattern using a difference in the solubility between the irradiated part and the non-irradiated part by irradiation with UV rays to greatly improve the uniformity of the film thickness upon coating of the thin film. In addition, the organic solvent according to the present invention can be used to wash the device, which comes into contact with the photosensitive material in the course of the microcircuit forming process, by removing the photosensitive material from the device. It also can remove the photosensitive material remaining on the undesired parts of the substrate on which the photosensitive material is coated.

TECHNICAL FIELD

The present invention relates to a resist composition that improvesuniformity of a thin film upon thin film-coating, necessary for alithographic process.

BACKGROUND ART

Rapid development of the semiconductor and the flat board displayindustry greatly has increased the demand for a resist composition usedmainly for semiconductors and flat board displays. Further, as the waferof a semiconductor as well as the substrate of the flat board displayare becoming larger in size, it has become more important to provide athin film with uniform thickness to reduce inferiority and increaseproductivity. As such resist composition, i) a positive photoresistcomposition containing a resin for forming a thin film, a sensitizershowing a sensitive response to light, and an organic solvent; and ii) anegative photoresist composition containing a resin, acid or radicalgenerating compound, a crosslinker and an organic solvent, are widelyused.

As the organic solvent for dissolving solid components of the aboveresist compositions and then coating them on the substrate, ethyleneglycol monoethylether acetate (hereinafter referred to as “EGMEA”) hadbeen widely used conventionally. The reason is that EGMEA can easilydissolve a resin and a sensitizer (or acid or radical generatingcompound) and can be safely stored for a long time. However, since anIBM report published that EGMEA can threaten biological safety, thenecessity to develop a new solvent harmless to humans has been on therise.

Compared with EGMEA, propylene glycol monomethylether acetate(hereinafter referred to as “PGMEA”) shows superior biological safety,has an excellent solubility of the resin and the sensitizer (or acid orradical generating compound) and has excellent coating uniformity uponthin film coating. Therefore, PGMEA has been used as the typical mainsolvent in this field up to now. However, as the size of the substrateto be coated increases, it is getting harder and harder to provide auniform film thickness from PGMEA alone.

DISCLOSURE OF INVENTION

The present invention is to provide a resist composition which isharmless to humans and can increase the uniformity of a thin film on alarge substrate by solving the above mentioned problems.

The purpose of the present invention is to provide a resist compositionwhich exhibits increased flowability upon coating, and increases theuniformity and storage stability of the thin film.

Another purpose of the present invention is to provide an organicsolvent for washing the device, which comes into contact with thephotosensitive material in the course of the microcircuit formingprocess, by removing the photosensitive material remaining on the deviceand for removing the photosensitive material remaining on the undesiredparts of the substrate on which the photosensitive material is coated.

The present invention provides a resist composition comprising benzylalcohol or its derivatives as an organic solvent. Specifically, thepresent invention provides a positive photoresist composition comprisingan alkaline soluble novolak resin, a naphthoquinonediazidephotosensitive compound and an organic solvent, characterized in thatthe organic solvent comprises benzyl alcohol or its derivatives; and anegative photoresist composition comprising an alkaline soluble acrylicresin or novolak resin, a strong acid or a radical generating compoundby irradiation with UV rays, a crosslinker and an organic solvent,characterized in that the organic solvent comprises benzyl alcohol orits derivatives.

Further, the present invention provides an organic solvent for removinga resist, wherein the organic solvent comprises benzyl alcohol or itsderivatives, which can remove the photosensitive material remaining onthe device, which comes into contact with the photosensitive material inthe course of the microcircuit forming process, to be used to wash thedevice and, which can remove the photosensitive material remaining onundesired parts of the substrate.

The organic solvent used in the present invention comprises benzylalcohol or benzyl alcohol derivatives. As the benzyl alcohol derivative,the compound which is prepared by a condensation reaction of benzylalcohol and ethylene oxide or propylene oxide and has a total molecularweight of at most 10,000 can be used. As the organic solvent, thesolvent containing only benzyl alcohol or its derivatives can be used.Further, the solvent wherein benzyl alcohol or its derivatives is mixedwith another solvent, such as PGMEA, ethyl lactate (hereinafter referredto as “EL”) and propylene glycol monomethyl ether (hereinafter referredto as “PGME”), can also be used. The solvent to be mixed with benzylalcohol or its derivatives are not limited to any particular one andsolvents of mixtures of two or more solvents can also be used.

In the organic solvents, the content of benzyl alcohol is preferably 1to 35% by weight and more preferably 5 to 30% by weight, based on 100%by weight of the organic solvent, irrespective of the kind of resist.

When the content of benzyl alcohol is less than 1% by weight or exceeds35% by weight, the coating uniformity is lowered and the flowabilitydecreases. However, when the content of benzyl alcohol falls within theabove range, the coating uniformity and the flowability are excellent.

<Positive Photoresist Composition>

In the resist compositions according to the present invention, thepositive photoresist composition is sensitive to UV rays, and the partirradiated by UV light is dissolved in a developing solution. Thiscomposition comprises an alkaline soluble novolak resin and anaphthoquinonediazide photosensitive compound in addition to the aboveorganic solvent. The novolak resin is a polymer material prepared byreacting an aromatic alcohol, such as phenol, cresol and xylenol, withformaldehyde in the presence of an acid catalyst. This resin is a basicmaterial forming a thin film, which is soluble in an alkaline solution.The photosensitive compound is a material sensitive to UV light andincludes triazines, imidazoles, acetophenones, naphthoquinone diazidesand the like.

In the present invention, preferably, the naphthoquinone diazidecompounds are used. This compound is prepared by ester reaction ofpolyhydroxybenzophenone and naphthoquinone diazide. The naphthoquinonediazide sulfonic acid ester is most preferred.

<Negative Photoresist Composition>

In the resist compositions according to the present invention, thenegative photoresist composition is sensitive to UV rays, and the partirradiated by UV light is not dissolved in a developing solution. Thiscomposition comprises an alkaline soluble acrylic resin or novolakresin, a strong acid or a radical generating compound by irradiationwith UV rays and a crosslinker in addition to the above organic solvent.The alkaline soluble acrylic resin may include a copolymer, such asmethyl meta acrylate, meta acrylic acid and n-butyl acrylate. Further,the strong acid or radical generating compound by irradiation with UVrays includes benzophenone derivatives, triazine derivatives orsulfonium derivatives. The crosslinker can include epoxy resin, epoxyacrylate resin, melamine resin, alkoxy benzene resin, diphenyl etherresin or styrene resin. The novolak resin is the same as that used inthe positive photoresist composition.

The resist composition according to the present invention can be coatedon a substrate by spin coating, roller coating, slit or spray coatingmethods to form a thin film coat.

Spin coating is a method of coating a thin film using centrifugal forcegenerated by rotation. For a semiconductor and lithography display, thismethod is mainly used. The bad flowability of the resist in this methodmakes the difference in the film thickness between the central and edgeportion of the substrate increase to lower the coating uniformity of thethin film. According to the present invention, since the flowability ofthe resist is excellent, such problem does not exist.

Roller coating is a method of coating a thin film while passing thesubstrate into a space between two rollers revolving in oppositedirections to each other. This method provides inferior uniformitycompared to a thin film formed by the revolving spin coating method.Also in the roller coating method, a plurality of grooves are presentedon the surface of roller. The resist covers the grooves and then itcarves in relief as it stands. After a period of time has passed, thecarved resist spreads out to make a coat. Accordingly, in order toobtain uniform film thickness from this method, the resist compositionshould spread out rapidly and uniformly. The resist compositioncontaining the organic solvent according to the present invention havinggood solubility and excellent uniformity can provide uniform filmthickness.

Slit and spray coating is a method to coat a resist by using nozzles ofseveral tens to hundreds micrometer. In this method, a quick and uniformdiffusion feature of the resist sprayed through nozzles becomes a veryimportant factor in the uniformity of the thin film.

The content of the solids component of the resist composition used inthe present invention is preferably 16 to 35% by weight for the spincoating, preferably 20 to 50% by weight for the roller coating, andpreferably 5 to 20% by weight for the slit coating.

Controlling the mixing ratio in the solvent when using the compositionof the present invention can maximize the improvement in processcapability, for example, an increase in a suitable exposure range, adecrease in a deviation in the film thickness upon formation of a coatedfilm, and a reduction in change in the fine line width due to adeviation in the baking temperature.

On the other hand, the photosensitive material may remain on the devicewhich comes to contact with the photosensitive material in the course ofthe microcircuit forming process and in addition, the photosensitivematerial may remain on an undesired part of the substrate in coating theresist composition on the substrate. For the former, it is necessary towash the device itself by removing the photosensitive material and forthe latter, it is also necessary to remove the photosensitive material.When the organic solvent comprising benzyl alcohol or its derivatives isused, such photosensitive material can be completely easily removed. Thereason is that the photosensitive material is highly soluble in theorganic solvent comprising benzyl alcohol or its derivatives. Since theorganic solvent used in the resist composition can also be used, it isadvantages as to cost and can be conveniently used.

The present invention will be discussed in detail with the followingexamples. However, it should not be interpreted that the scope of theinstant invention is limited to only the examples.

BEST MODE FOR CARRYING OUT THE INVENTION Example 1

A solid comprising of 70% by weight of cresol novolak resin having aweight-average molecular weight of 7,000 prepared by a condensationreaction of cresol and formaldehyde with an oxalic acid catalyst and 30%by weight of naphthoquinone diazidosulfonic ester as a photosensitivecompound was mixed with a mixture of 99% by weight of PGMEA and 1% byweight of benzyl alcohol (hereinafter referred to as “BA”) in a 2.5:7.5ratio (by weight) to be dissolved. The resulting product was filteredthrough the 0.2 um filter and as a result, a resist composition wasprepared.

Example 2

The resist composition was prepared in the same manner as in Example 1except that a mixture of PGMEA and BA in a ratio of 95:5% by weight wasused as an organic solvent.

Example 3

The resist composition was prepared in the same manner as in Example 1except that a mixture of PGMEA and BA in a ratio of 90:10% by weight wasused as an organic solvent.

Example 4

The resist composition was prepared in the same manner as in Example 1except that a mixture of PGMEA and BA in a ratio of 80:20% by weight wasused as an organic solvent.

Example 5

The resist composition was prepared in the same manner as in Example 1except that a mixture of PGMEA and BA in a ratio of 70:30% by weight wasused as an organic solvent.

Example 6

The resist composition was prepared in the same manner as in Example 1except that a mixture of PGMEA and BA in a ratio of 65:35% by weight wasused as an organic solvent.

Comparative Example 1

The resist composition was prepared in the same manner as in Example 1except that 100% by weight of PGMEA was used as an organic solvent.

After coating the resist composition according to examples 1 to 6 andcomparative example 1 on a glass substrate having a 370 mm wide by 470mm long and 0.7 mm thick, by using the spin coating method, a deviationin the film thickness was measured using a NANOSPEC M 6500 instrument, adevice for measuring film thickness. The results are shown in table 1.TABLE 1 Thin-film coating characteristics of the photosensitive resinaccording to the kind of solvent Coating Uniformity(%) Length of flow(mm) Example 1 3.13% 23 Example 2 2.92% 31 Example 3 2.75% 47 Example 42.97% 38 Example 5 2.93% 32 Example 6 3.05% 30 Comparative 3.16% 21Example 1

As can be seen in the above Table 1, the resist compositions accordingto Examples 1 to 6 of the present invention comprising benzyl alcoholhave excellent coating uniformity and flowability as compared with theresist composition of comparative example 1 which does not includebenzyl alcohol.

Example 7

A solid comprising of 24% by weight of an alkaline soluble acrylic resinhaving a weight-average molecular weight of 20,000-40,000, 14% by weightof multifunctional acrylic monomer, 5% by weight of an alpha aminoketone radical photo initiator and 57% by weight of an organic pigmentwas mixed with a mixture of 99% by weight of PGMEA and 1% by weight ofbenzyl alcohol in a 2.0:8.0 ratio (by weight) to be dissolved. Theresulting product was filtered through the 0.2 um filter and as aresult, a resist composition was prepared.

Example 8

The resist composition was prepared in the same manner as in Example 7except that a mixture of PGMEA and BA in a ratio of 95:5% by weight wasused as an organic solvent.

Example 9

The resist composition was prepared in the same manner as in Example 7except that a mixture of PGMEA and BA in a ratio of 90:10% by weight wasused as an organic solvent.

Example 10

The resist composition was prepared in the same manner as in Example 7except that a mixture of PGMEA and BA in a ratio of 80:20% by weight wasused as an organic solvent.

Example 11

The resist composition was prepared in the same manner as in Example 7except that a mixture of PGMEA and BA in a ratio of 70:30% by weight wasused as an organic solvent.

Example 12

The resist composition was prepared in the same manner as in Example 7except that a mixture of PGMEA and BA in a ratio of 65:35% by weight wasused as an organic solvent.

Comparative Example 2

The resist composition was prepared in the same manner as in Example 7except that 100% by weight of PGMEA was used as an organic solvent.

After coating the resist composition according to examples 7 to 12 andcomparative example 2 on a glass substrate being a 370 mm wide by 470 mmlong and 0.7 mm thick, by using the spin coating method, a deviation inthe film thickness was measured using a NANOSPEC M 6500 instrument, adevice for measuring film thickness. The results are shown in table 2.TABLE 2 Thin-film coating characteristics of the photosensitive resinaccording to the kind of solvent Coating Uniformity(%) Length of flow(mm) Example 7 3.98% 22 Example 8 3.01% 35 Example 9 2.35% 49 Example 102.54% 40 Example 11 2.75% 36 Example 12 3.04% 32 Comparative 4.03% 20Example 2

As can be seen in the above Table 2, the resist compositions accordingto Examples 7 to 12 of the present invention containing benzyl alcoholhave excellent coating uniformity and flowability as compared with theresist composition of comparative example 2 not containing benzylalcohol.

Example 13

The photoresist material, naphthoquinone diazidesulfonic acid ester, isadded into 100 g of organic solvent solution, i.e., a mixed solution ofPGMEA and BA in ratio of 99 wt. %:1 wt. %, 95 wt. %:5 wt. %, 90 wt. %:10wt. %, 80 wt. %:20 wt. %, 60 wt. %:40 wt. %, 40 wt. %:60 wt. %, 20 wt.%:80 wt. % or a solution consisting of PGMEA 100 wt. %, and stirred at200 rpm. The maximum amount of the photosensitive material dissolved forone hour is measured. The results are shown in Table 3 below. TABLE 3Solubility of the photosensitive material according to the kind ofsolvent PGMEA (unit: wt. %) BA (unit: wt. %) Solubility (unit: g) 99 12.5 95 5 4 90 10 8 80 20 50 60 40 50 40 60 70 20 80 80 100 0 2

As a result of the experiment, it has been shown that the organicsolvent comprising benzyl alcohol has significantly superior solubilityof the photosensitive material as compared with the organic solvent notcomprising benzyl alcohol.

Effect of Invention

The resist composition comprising benzyl alcohol or its derivatives asan organic solvent, which is coated on the substrate, provides excellentflowability upon formation of a thin film, reduced deviation in the filmthickness and increased coating uniformity. Further, this organicsolvent is useful either in washing the device in situ or in removingphotosensitive material remaining on the undesired part upon coating,which makes a lithography process economical and convenient.

1. A resist composition comprising an alkaline soluble novolak resin, anaphtoquinonediazide photosensitive compound and an organic solvent,characterized in that the organic solvent comprises benzyl alcohol orits derivatives.
 2. The resist composition according to claim 1,characterized in that the organic solvent comprises 1% by weight to 35%by weight of benzyl alcohol or its derivatives.
 3. A photosensitiveresist composition comprising an alkaline soluble acrylic resin ornovolak resin, a strong acid or a radical generating compound byirradiating UV ray, a crosslinker and an organic solvent, characterizedin that the organic solvent comprises benzyl alcohol or its derivatives.4. The resist composition according to claim 3, characterized in thatthe organic solvent comprises 1% by weight to 35% by weight of benzylalcohol or its derivatives.
 5. An organic solvent for removing a resist,comprising benzyl alcohol or its derivatives.